We propose to evaluate the expression of idiotypic determinants on functional subpopulations of T lymphocytes. In addition, we shall evaluate the requirements for H-2 restriction in these cell populations. Recent experiments performed in our laboratory have used genetic, fine specificity and idiotypic analysis to demonstrate NPb idiotypic determinants on NP(4-hydroxy-3-nitrophenyl acetyl) DTH effector T cell and on NP specific suppressor T cell populations. We propose to expand these studies to investigate the nature of the T cell receptor on subpopulations of T cells which mediate contact sensitivity reactions, antigen specific proliferative reactions, feedback suppression, cell mediated cytolysis and antigen specific helper responses. Another aim of these studies is to investigate the modulation of the immune response with anti-idiotypic reagents. Thus, anti-idiotypic antisera will be used to trigger various functional T cell populations and we will use anti-idiotype or idiotype coupled cells to generate idiotype specific suppressor cells. This will allow us to investigate the immune network interactions postulated by Jerne.